Solid bowl screw centrifuge comprising a peeling disk, and method for the operation thereof

ABSTRACT

A solid bowl screw centrifuge includes a centrifuging chamber and a rotatable drum having a horizontal axis of rotation. The rotatable drum surrounds the centrifuging chamber. Also included is a rotatable screw arranged in the rotatable drum, at least one solids discharge, at least one liquid discharge duct and a peeling disk via which liquids are discharged through the liquid discharge duct. Further included is a blocking chamber connected to an output side of the peeling disk.

The invention relates to a solid bowl screw centrifuge according to thepreamble of Claim 1 and to a method for its operation.

The solid bowl screw centrifuge disclosed in German Patent Document DE43 20 265 A1 is equipped with a weir on the liquid outlet side, whichweir has a passage. An orifice plate, which is stationary relative tothe drum during its rotation, is assigned to the passage. By way of athreaded bush, this orifice plate is axially displaceable. By rotatingthe threaded bush, the distance between the weir and the orifice platecan be changed. The resulting change of the outflow cross-section causesa change of the liquid level in the centrifugal drum, so that acontinuous adjustment of this liquid level can be achieved by displacingthe orifice plate.

From German Patent Document DE 39 04 151 A1, a diaphragm plate situatedon the screw is known. Nozzles on the outer circumference are used forminimizing the energy consumption. A processing of sensitive productswith a gas-tight sealing-off with respect to the environment cannot beachieved by means of this construction.

From German Patent Document DE 198 30 653 C1 of the above-mentionedtype, it is known to implement the liquid discharge of an open solidbowl screw centrifuge by means of a peeling disk which is followed by alabyrinth seal, in order to return product droplets to the peeling disk.According to this construction, no sealing-off is required with respectto the exterior space. However, solid bowl screw centrifuges withpeeling disks in the case of which the product space is sealed offtoward the outside are also in demand. It is an object of the inventionto implement such a solid bowl screw centrifuge by means of simpleconstructive devices.

The invention achieves this task by means of the object of Claim 1.Accordingly, the chamber has an annulus with a first blocking and siphondisk arranged therein. The chamber is a hydrohermetic blocking chamberfor sealing off the centrifuging chamber against the surroundings bymeans of a sealing liquid to which a feed line is directly assigned forthe separate sealing liquid independent of the centrifuge material.

By means of the invention, a simple method of operating the centrifugeaccording to the invention is to be provided. This is indicated in Claim15. Accordingly, a separate sealing liquid independent of the centrifugematerial is fed through a feed line into the hydrohermetic blockingchamber—for sealing off the centrifuging chamber with respect to thesurroundings.

The screw preferably has a siphon disk which extends from the screwradially to the outside into the centrifuging chamber.

In a constructively simple and cost-effective manner, the blockingchamber with the sealing liquid supply—preferably in combination withthe two blocking or siphon disks—permits a reliable sealing-off of thecentrifuging chamber with respect to the surrounding atmosphere. Incontrast, in German Patent Document DE 198 30 653 C1 of theabove-mentioned type, the product can still come in contact with thesurrounding atmosphere because of the labyrinth seal.

Blocking chambers are also known per se from centrifuges with a verticalaxis of rotation, a separate sealing liquid also being guided into theseblocking chambers (German Patent Document DE 196 31 226). Blockingchambers in the case of such separators are also known from GermanPatent Document DE 657 473. However, it has not been considered andapparently also not been seen as being advantageous to implement ablocking chamber also in the case of centrifuges with a horizontal axisof rotation which blocking chamber is acted upon by a separate sealingliquid independent of the centrifuge material.

When a pressure is built up in the interior of the decanter or of thesolid bowl screw centrifuge, a gas (such as CO2) dissolved in thecentrifuge product (for example, a beverage) would under certaincircumstances partially escape from the solid bowl screw centrifugewithout the blocking chamber arrangement with two siphon disks and thesealing liquid feed. This is prevented by the invention.

By means of the blocking or siphon disk in the blocking chamber,sufficient pressure can be built up in a simple manner, so that a gas,such as CO2, is kept in the liquid (phase). By varying the diameter ofthe blocking and siphon disk, the pressure in the blocking chamber canbe varied, which preferably amounts to up to 4 bar, particularly 0.5 to2.5 bar. The pressure influences the type of the conveyance of thesolids and/or their consistency.

Particularly preferably, the feed line and a discharge bore lead into anannulus of the blocking chamber and permit the continuous feeding anddischarging of the sealing liquid into the blocking chamber and out ofthe blocking chamber. As a result, a continuous cleaning of the blockingchamber can be implemented in a much simpler manner than in GermanPatent Document DE 196 31 226 A1, and, as a result, the forming ofdeposits in the blocking chamber can be effectively prevented. Thecentrifuge therefore also meets high hygienic requirements.

Since the liquid discharge takes place by means of a peeling disk whichis followed, particularly in a direct manner, by the blocking chamber, adissolved gas, such as CO2, can be kept at least largely in the liquidto be discharged or to be processed, which considerably simplifies theprocessing of products, such as beer.

In particular, the blocking chamber as well as the peeling disk arearranged on the drum side or toward the drum with respect to the mainbearing of the drum, which permits a very simple further development ofthe construction. This results not only in a durable sealing-off withrespect to the surrounding atmosphere but, under certain circumstances,also in a sealing-off with respect to product contamination by oil mistof the liquid-side main bearing (not shown here).

Additional advantageous further developments are contained in theremaining subclaims.

In the following, the invention will be explained in detail by means ofembodiments with respect to the drawing.

FIG. 1 is a sectional view of a solid bowl screw centrifuge according tothe invention; and

FIG. 2 is an enlargement of the cutout from FIG. 1.

FIG. 1 illustrates a solid bowl screw centrifuge 1 with a drum 3 havinga horizontal axis of rotation in which a screw is arranged. The drum 3and the screw 5 each of an essentially cylindrical section and a sectionwhich conically tapers here.

An axially extending centric feed pipe 7 is used for feeding thecentrifuge material 8 by way of a distributor 9, which here isperpendicular with respect to the feed pipe 7, into the centrifugingchamber 11 between the screw 5 and the drum 3.

When, for example, a sludgy pulp is fed into the centrifuge, solidparticles are deposited on the drum wall. A liquid phase developsfarther toward the inside.

The screw 5 disposed by means of the bearing 6 rotates at a slightlylower or higher speed than the drum 3 and conveys the centrifuged solidsS toward the conical section out of the drum 3 to a solids discharge(not shown here).

In contrast, the liquid flows to the larger drum diameter at therearward end of the cylindrical section of the drum 3 and is guidedthere through a weir 15 into a chamber 17 which axially adjoins theactual centrifuging chamber and has a diameter which is smaller incomparison to the centrifuging chamber.

A peeling disk 19 for discharging the liquid phase L is arranged in thechamber 17 (see also FIG. 2), which is adjoined by a discharge duct 20discharging the liquid phase L from the drum 3. The peeling disk 19 isarranged directly on the feed pipe 7 which is stationary during theoperation, a sealed-off gap-free arrangement being implemented betweenthe peeling disk 19 and the feed pipe 7.

Preferably in the conically tapering area of the drum 3, the screw 1—infront of the solids discharge (not shown here)—has a first siphon disk21 which extends from the screw 5 radially toward the outside into thecentrifuging chamber 11 and is immersed into the liquid level P1.

As a result of the immersion, the interior area or the centrifuging areain the centrifuging chamber 11 (here, to the right of the siphon disk21) are hermetically sealed off with respect to the surroundings or thesurrounding atmosphere. It would also be conceivable to arrangeadditional siphon disks in the conical area of the drum 3 in order toinfluence the consistency of the solids in this manner (not shown here).

In the chamber 17, a ring shoulder 23 is arranged on the side of thepeeling disk 19 pointing to the centrifuging chamber, which ringshoulder 23 extends radially from the inner circumference of the chamber17 toward the inside.

A liquid level P1 forms between the first siphon disk 21 and the ringshoulder 23 during the operation of the centrifuge because the siphondisk 21 and the ring shoulder overlap in the radial direction or becausethe two elements are correspondingly adapted to one another.

In contrast, between the ring shoulder 23 situated closer to the peelingdisk 19 and the peeling disk 19, the liquid level P2 extends to theinlet opening 25 of the peeling disk. The liquid level can be variedhere by slightly (? translator) throttling the peeling disk 19.

On the side of the peeling disk 19 facing away from the ring disk 23(shoulder? translator), the chamber 17 extends radially toward theinside to close to the feed pipe or to a diameter smaller than thediameter of the screw 5, and leads into an axial passage 27 which isadjoined in the axial direction by an annulus 29 which acts as ablocking chamber and which, in turn, leads into an axial discharge duct31 for the sealing liquid on the outer circumference of the feed pipe 7and of the discharge duct 31 for the centrifuge material, the insidediameter of the discharge duct 31 for the sealing liquid being smallerthan the inside diameter of the passage 27, so that sealing liquidoverflowing from the blocking chamber 19 flows out through the dischargeduct 31.

In the blocking chamber or in the annulus 29, another siphon or blockingdisk 33 is stationarily arranged on its inner circumference and extendsfrom the inside radially to the outside into the blocking chamber.

An feed line 35—here arranged parallel to the feed pipe 7 on its outercircumference—leading into the centrifuge from the outside permits thedirect feeding of sealing liquid, such as water, which is independent ofthe centrifuge material, from the inside into the blocking chamber 29.

A discharge bore 37—here, leading on the circumference of the annulus 29at an acute angle with respect to the axis of rotation radially to theoutside out of the drum 3—permits the continuous discharge of sealingliquid from the annulus 29, which causes an advantageous cleaning.

During the operation—that is, during rotations of the drum 3 and thescrew 5—a liquid level P3 of the sealing liquid forms in the annulus 29,which liquid level P3 seals off the interior of the drum 3 against thesurrounding atmosphere when the feeding amount of sealing liquid intothe blocking chamber is larger than the discharge amount, which isadjusted by the dimensioning of the discharge bore 37. Excess waterwhich does not flow off through the discharge bore 37 flows off throughthe discharge duct 31.

By means of the second siphon disk 33 in the blocking chamber 29,however, a sufficient pressure can be built up in a simple manner, sothat gas is kept in the liquid. By varying the diameter of the blockingand siphon disk 33, the pressure in the blocking chamber 29 can bevaried. The pressure influences the type of the conveyance of the solidsand/or their consistency.

LIST OF REFERENCE NUMBERS

-   Solid bowl screw centrifuge 1-   bearing 2-   drum 3-   screw 5-   feed pipe 7-   centrifuge material 8-   distributor 9-   centrifuging chamber 11-   discharge duct 13-   weir 15-   chamber 17-   peeling disk 19-   discharge duct 20-   blocking and siphon disk 21-   ring shoulder 23-   inlet opening 25-   passage 27-   annulus 29-   discharge duct 31-   blocking and siphon disk 33-   feed line 35-   discharge bore 37-   liquid level P1, P2, P3-   centrifuge material S

1. A solid bowl screw centrifuge, comprising: a centrifuging chamber; arotatable drum having a horizontal axis of rotation, the rotatable drumsurrounding the centrifuging chamber; a rotatable screw arranged in therotatable drum; at least one solids discharge; at least one liquiddischarge duct; a peeling disk via which liquids are discharged throughthe liquid discharge duct; a blocking chamber connected to an outputside of the peeling disk, the blocking chamber including an annulushaving a first siphon disk arranged therein, the blocking chamber beinga hydrohermetic blocking chamber to seal off the centrifuging chamberfrom its surroundings via a sealing liquid that is independent ofmaterial to be centrifuged; a feed line assigned to the blocking chamberto feed the sealing liquid; and wherein the rotatable screw includes asecond siphon disk extending from the screw radially to the outside intothe centrifuging chamber.
 2. (canceled)
 3. The solid bowl screwcentrifuge according to claim 1 wherein the blocking chamber isconnected directly behind the peeling disk.
 4. The solid bowl screwcentrifuge according to claim 1, wherein the second siphon disk isarranged on the screw in front of the solids discharge.
 5. The solidbowl screw centrifuge according to claim 4, wherein the second siphondisk is arranged on the screw in a conically tapering section of therotatable drum.
 6. The solid bowl screw centrifuge according to claim 1,further including a feed pipe and a discharge bore leading into theannulus and permitting a continuous feeding and discharging of thesealing liquid into and out of the blocking chamber.
 7. The solid bowlscrew centrifuge according to claim 1, wherein the rotatable drum andthe rotatable screw each have an essentially cylindrical section and atapering section, the centrifuge further including a peeling diskchamber adjoining the cylindrical section, the peeling disk chamberhaving a diameter that is smaller than a diameter of the centrifugingchamber and in which peeling disk chamber the peeling disk is situated.8. The solid bowl screw centrifuge according to claim 7, wherein a ringshoulder is arranged on an inner circumference of the peeling diskchamber.
 9. The solid bowl screw centrifuge according to claim 7,wherein the peeling disk chamber, on a side of the peeling disk facingaway from the ring shoulder, extends radially to the inside of therotatable drum to a diameter which is smaller than the diameter of thescrew, and the peeling disk chamber leads into a passage which isadjoined in an axial direction by the annulus leading into an axialdischarge duct for the sealing liquid, the inside diameter of dischargeduct being smaller than that of the passage, so that sealing liquidoverflowing from the blocking chamber 29 can be discharged through thedischarge duct.
 10. The solid bowl screw centrifuge according to claim1, wherein the first siphon disk is one of attached and moldedperpendicularly to an inner circumference of the blocking chamber havingthe annulus, which first siphon disk extends radially from the insidetoward the outside of the drum and into the annulus.
 11. The solid bowlscrew centrifuge according to claim 1, wherein the feed line is arrangedparallel to and on an outside circumference of a feed pipe for feedingmaterial to be centrifuged.
 12. The solid bowl screw centrifugeaccording to claim 1, wherein a discharge bore leads from an outercircumference of the annulus at an acute angle with respect to an axisof rotation of the drum and radially to the outside of the drum.
 13. Thesolid bowl screw centrifuge according to claim 8, wherein the firstsiphon disk and the ring shoulder are mutually coordinated such that,during an operation of the centrifuge, a liquid level P₁ forms betweenthem.
 14. The solid bowl screw centrifuge according to claim 11, whereinthe peeling disk is arranged in a sealed-off manner on the feed pipewhich is stationary during an operation of the centrifuge.
 15. A methodof operating a solid bowl screw centrifuge, the solid bowl centrifugeincluding a centrifuging chamber, a rotatable drum surrounding thecentrifuging chamber and having a horizontal axis of rotation, arotatable screw arranged in the rotatable drum, at least one solidsdischarge, at least one liquid discharge duct, a peeling disk via whichliquids are discharged through the liquid discharge duct, a blockingchamber connected to an output side of the peeling disk including anannulus having a first siphon disk arranged therein, a feed lineassigned to the blocking chamber to feed the sealing liquid, and therotatable screw includes a second siphon disk extending from the screwradially to the outside into the centrifuging chamber, the method stepscomprising, turning on the centrifuge; and feeding a sealing liquid thatis independent of the material to be centrifuged through the feed lineinto the blocking chamber to seal off the centrifuging chamber from itssurroundings.
 16. The method according to claim 15, further includingthe step of discharging the sealing liquid, thereby effecting acontinuous cleaning of the blocking chamber.
 17. The method according toclaim 15, further including the step of adjusting pressure in theblocking chamber by varying a diameter of the first siphon disk.
 18. Themethod according to claim 15, further including the step of providing apressure in the centrifugal chamber of up to 4 bar.
 19. The methodaccording to claim 15, further including the step of providing apressure in the blocking chamber of 0.5 to 2.5 bar.